The RIGHT WAY to test and repair your A/C leak

Most people think the way to test for a leak is with a vacuum pump ,WRONG ! The reason this is wrong is because if you have a bad seal it will suck it in and show NO leak Remember the freon is being pushed out not in . So here is the Correct way to find a leak you'll need a bottle of nitrogen and a nitrogen gauge , your system will be probaly empty , so... connect your gauge to the LOW side of your A/C then load your A/C until the ball drops on the gauge ,turn the **** on the gauge off ...wait a few minutes come back and turn it on again .... if you see the ball move at all you have a leak ! Now being nitrogen is very thin YOU WILL HEAR the leak ,repair the leak and your sealed system will be as good as new ...Now you can use a vacuum pump to evacuate your system and let it pump down for at least a hour to remove all contaminents like moisture and acid these are your A/C 's enemys

but can you hear a evap leak ? there is NO guessing using Nitrogen .just ask the guy who did my mothers Caravan ! i asked him if he used nitrogen and he told me his 35 year mechanic was the BEST 2 weeks later it was empty and i made him change the evap for FREE , i told him i did a/c for 15 years and he told me i was wrong , well it cost him 975 bucks ! UV dye gets to be very messy , i've used it before ,it doe's have its application ,but nitrogen is a first time fix all the first time . believe me , when your climbing a 40ft ladder you don't want to be climbing up and down every week . when i fix a car with R-12 i charge a $100.00 a lb thats because they don't make it ! so before you couldn't buy it i bought 10 -100 lb cylinders at .50 a pound . no room for mistakes for the customer at 100 bucks a lb !

Only a shoddy A/C mechanic would only check for leaks using vacuum. It is but one stage of a leak detection process. The other involves filling the system with a normal A/C charge and using a sniffer.
Dye is just fine for finding tricky leaks. Get car in, do a quick charge with gas/dye and get the car back in a few weeks.
Problem with using a gas with a lower molecular weight than the refrigerant is: you don't know if the leak would allow refrigerant to pass or not. What may be a leak to nitrogen may be no issue to refrigerant.

Only a shoddy A/C mechanic would only check for leaks using vacuum. It is but one stage of a leak detection process. The other involves filling the system with a normal A/C charge and using a sniffer.
Dye is just fine for finding tricky leaks. Get car in, do a quick charge with gas/dye and get the car back in a few weeks.
Problem with using a gas with a lower molecular weight than the refrigerant is: you don't know if the leak would allow refrigerant to pass or not. What may be a leak to nitrogen may be no issue to refrigerant.

being the nitrogen is thinner than Freon it passes through the smallest pin hole . freon is getting expensive i now get $100 a lb for R-12 . years ago before they stopped making R-12 i bought 10 -100 lb cylinders , so when doing a R-12 leak test it gets very expensive to put in then dump the charge out plus nitrogen you can hear the leak when you can't hear freon leaking . inexpensive 1 st time fix solution i've been doing this for 15 years as a roof top A/C tech . the guy at my supply house turned me on to this method

My AC system has leaked out, and now has not been in use for years. Where does one buy nitrogen? BTW I live in Canada. Also some told me putting in other gasses into your AC system, contaminates it. Hence mechanics will not want to work on the system after that, as their systems use 134a tanks.

one... you bumped a 2 year old thread...
two.... If your worried about mechanics wanting to touch your car just bring it to one so they can find the leak.
three... if your A/C hasnt worked in years your going to have leaks EVERYWHERE. The o-ring will have dried up and most likely there is corrosion in your system.

Your best bet is to just start buying all the major parts, compressor, evap, condenser, dryer and lines. Install it all with New o-rings, valve cores, and a new orifice tube.
Vac your system, add freon and inject oil with dye...

For the average guy with one or two cars I'm not seeing any advantage to going out and purchasing nitrogen and the means to inject it into your vehicle.

Also for the average guy you're not going to go out and buy an electronic HC leak detector. Just isn't cost effective unless you just like buying tools or have more money than you know what to do with.

Nitrogen isn't not going to contaminate anything as once you've used it for finding the leaks it gets sucked out of the system when the system is evacuated. You just need to make sure whoever is vacuuming your system isn't recovering it like freon into their machine and injecting it back into your system. Your ACs system performance with part nitrogen would suck.

Realistically in the real world you pump in freon or freon with a dye and search for the leaks. Oily joints or areas of a component that appear dirty and oily are the areas to check first. Using dye with a black light is usually the easiest way to locate them. Repair the leaks and take it to someone to evacuate and recharge the system.